Stars and stellar evolution
Cosmic dust does far more than float through space. It's the raw material from which stars, planets and possibly even life emerge. Yet astronomers have long puzzled over where this vast amount of dust comes from and what it's made of.
The beautiful supernova remnant looks a little different from other examples of stars that detonated in the past. And it should, because according to astronomers, the star that met its end exploded twice. It was a white dwarf in its former life, pulling material from a binary companion, creating the perfect conditions for a Type 1a supernova. It accumulated a blanket of helium, which exploded first, triggering a second detonation at the core of the star.
Pulsars are spinning neutron stars, with several times the mass of the Sun compressed into a sphere just 10 km across. They have a theoretical "death line,” a point where pulsars should stop emitting radio waves as they slow down. But researchers have detected two pulsars still beaming radio signals despite being below this death line. One explanation is that there are tiny irregularities on their surfaces, mountains just 1 cm tall. These peaks amplify local electric fields, making it easier for the pulsars to accelerate particles and produce radio emissions that should be impossible.
Very massive stars (VMSs), which typically has masses about 100 times that of our own Sun, are critical components in our understanding of the formation of important astronomical structures like black holes and supernovae. However, there are some observed characteristics of VMSs that don’t fit the expected behavior based on the best models we have of them. In particular, they hover around a relatively limited band of temperatures, which are hard to replicate with typical stellar evolution models. A new paper from Kendall Shepherd and their co-authors at the Institute for Advanced Study (SISSA) in Italy describes a series of new models based on updated solar winds that better fit the observations of VMSs in their natural environment, and might aid in our understanding of the development of some of the most fascinating objects in the Universe.
Gas clouds in the Milky Way's Galactic Center contain copious amounts of star-forming gas. But for some reason, few massive stars form there, even though similar gas clouds elsewhere in the galaxy easily form massive stars. The clouds also form fewer stars overall. Are they a new type of molecular cloud?
Just when astronomers think they're starting to understand stellar activity, something strange grabs their attention. That's the case with a newly discovered stellar object called ASKAP J1832-0911. It lies about 15,000 light-years from Earth and belongs to a class of stellar objects called "long-period radio transients." That means it emits radio waves that vary in their intensity on a schedule of only 44 minutes per cycle. It does the same thing in X-ray intensities, which is the first time anybody's seen such a thing coupled with long-period radio transits.
Betelgeuse is dying—but not quietly. This colossal red supergiant, already famous for its brightness fluctuations, has now revealed a strange long-term rhythm: a secondary pulse every 2,100 days. One tantalising theory suggests a hidden companion—possibly a second star orbiting Betelgeuse at roughly the distance between Saturn and the Sun, circling every six years. Astronomers recently pointed the Hubble Space Telescope at the giant in search of this elusive "Betel-Buddy" but failed to find it constraining its size and orbit.
Astronomers have spotted a pulsar in a binary system, taking about 3.6 hours for the stars to orbit one another. Their orbit is so close that, from our vantage point, the pulsar's radio signals vanish for roughly one-sixth of each cycle—blocked by the companion's interference. Researchers think that the more massive star died first, exploding as a supernova and collapsing into a neutron star, passing within the atmosphere of the other. It took about 1,000 years to blow away the envelope of material.
Over the past 90 years, astronomers have successfully matched several Chinese historical records of "guest stars" with known supernovae. However, identifying historical novae (smaller stellar explosions) has proven to be far more challenging, with many proposed candidates later turning out to be comets or meteors instead. One particularly debated case involves a guest star recorded in 1408 CE by Chinese astronomers. A team of astronomers now think they may have finally been able to identify the event, a rare nova that could potentially solve this centuries old astronomical mystery.
The satellite population in Low-Earth Orbit (LEO) is not an open book. While data on many satellites is public, others are shrouded in secrecy, and information is incomplete for others. New research shows how observers can determine satellite shapes by watching them occult background stars.
Gamma-ray bursts (GRBs) are the most powerful phenomena in the Universe. First detected during the Cold War, these events beam a tremendous amount of high-energy light our way in a short period of time. They come in two types: short GRBs that last for less than two seconds and long GRBs that last for minutes. Both types have mysterious origins. Short GRBs could be caused by the collisions of neutron stars or perhaps the powerful flares of a magnetar. Observations of long GRBs suggest they are caused by a powerful supernova called a hypernova, where a massive star collapses to become a black hole. But a new study suggests that the origins of long GRBs are more diverse.
Tracking the sources of photons is a hobby of many astrophysicists. Some types of photons are tied so closely to particular phenomena that tracking their sources would help answer some larger questions in astrophysics itself. Photons on the "511 keV line" are one such type of photon, and they have been overrepresented near the galactic core, with no known source being prolific enough to create them. A new paper from Zachary Metzler and Zorawar Wadiasingh of the University of Maryland and NASA's Goddard Space Flight Center suggests one potential source - millisecond pulsar (MSP) binaries.
The most massive stars in the Milky Way contain one hundred times more mass than the Sun, even more in some cases. These O-type stars are extremely hot, luminous, and blue, and often die in supernova explosions. Astrophysicists want to know how they get so big, and a simple household chemical might hold the answer.
The JWST continues to live up to its promise by revealing things hidden from other telescopes. One of its lesser-known observations concerns Free-Floating Planets (FFP). FFPs have no gravitational tether to any star and are difficult to detect because they emit so little light. When the JWST detected 42 of a particular type of FFP in the Orion Nebula Cluster, it gave astronomers an opportunity to study them more closely.
NASA's Chandra X-ray Observatory has released new 3D models of space objects that many Universe Today readers will be familiar with. The list includes the supernova remnants Cassiopeia A, G292.0+1.8, the Cygnus Loop, and the young T Tauri star BP Tau. The models are based on observations from space telescopes, theoretical models, and computational algorithms.
A team of researchers led by the Los Alamos National Laboratory examined the possibility that the jets coming from collapsing stars could be responsible for creating the heaviest elements in the Universe.
Stars don't exist in isolation. They have siblings and exist in clusters, associations, and groups. The ESA's Gaia mission found an unusual group of stars rapidly leaving its birthplace behind and dispersing into the wider galaxy. While that's not necessarily unusual behaviour, it is for such a large group. Could supernovae explosions be responsible?
Star birth is a process hidden inside dense crèches of gas and dust. Yet, if you know what to look for, you can see the products of this essential cosmic process across the sky. The Circinus West molecular cloud is a starbirth crèche some 2,500 light-years away. It boasts everything from dark nebulae to protostellar objects and newborn stars to the faint ghosts of stars that have already died.
The planets in our Solar System orbit the Sun along a plane extending from the solar equator. That's typically the case for exoplanets too but just recently, a team of astronomers have found a system where a planet is in a perpendicular orbit around a binary pair! The brown dwarf system with its strange planetary companion is likely the result of three-body interactions between the stars and planet, tweaking it into the crazy orbital configuration we see today.
The solar system is currently embedded deep within the Local Bubble, a region of relatively low density stretching for a thousand light-years across. It was carved millions of years ago by a chain of supernova explosions. And the evidence for it is right under our feet.
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